Diode lasers as well as Carbon dioxide (12C16O2) lasers are used as incision and ablation surgical tools to treat soft tissue in dentistry as well as in oral maxillofacial surgery. The reasons that lasers are used for soft tissue incisions include a lack of bleeding, high cutting precision and minimal collateral damage. The surgical site is also automatically sterilized and post operative edema is considerably reduced, while healing is faster, as compared to non-laser surgery.
Precise incision with diode lasers is described in U.S. Pat. No. 4,736,743. The Carbon Dioxide lasers broadly utilized in dentistry and oral surgery emit radiation at a wavelength of 10.6 microns. The radiation emitted by the lasers penetrates 30-50 microns deep into tissue, depending on the water content of the tissue. The laser beam is usually focused on the tissue with a focusing lens, often made of ZnSe, which generates a spot size of 80-150 microns. The laser provided hemostatic incisions at power levels ranging from approximately 5-20 W for a continuous working laser, at variable speeds. The laser can also be operated in a superpulse mode such as produced by Sharplan with a train of individual pulses of approximately 100-300 microseconds duration and a peak power ranging from approximately 300 to 1000 W and repetition rates of approximately 50-300 pps. When operated in a superpulse mode, the thermal damage created by the thermal diffusion of absorbed heat is minimized and is close to 50-100 microns. Since the thermal relaxation time of tissue at 50 microns depth is approximately 200 microseconds, further reduction of pulse duration does not substantially further reduce collateral damage. Another pulse mode utilized with CO2 lasers is the ultra pulse produced by Coherent USA. The energy content of ultrapulses is usually close to 50-500 millijoules/pulse.
The applications of a CO2 laser in oral surgery include gum treatment (e.g. gingivectomy and other periodontal procedures), implant exposure in second stage implantology (excluding first stage implantology) and many other oral treatments. The procedures are very common. [See for example “Use of the CO2 Laser in Soft Tissue Periodontal Surgery,” M. Israel, Practical Periodontics & Aesthetic Dentistry, Vol. 6, No. 6, pp. 57; “The Role of Lasers in Ambulatory Oral Maxillofacial Surgery,” Barak et al, Operative Techniques in Otolaryngology—Head and Neck Surgery, Vol. 5, No. 4, 1994; and “The Use of Lasers in Implantology: An overview,” Walsh, Journal of Oral Implantology, Vol. XVIII (4), 1992.]
When using a conventional 12C16O2 laser, surgeons are aware of the necessity to be very careful not to penetrate too deep into gum tissue in order to avoid any damage to the underneath bone or of the tooth hard tissue. That is one of the reasons that lasers, e.g. 12C16O2 lasers, are not used to expose bones in the first implantology stage since heat, which may diffuse from the incision made with a 12C16O2 laser, may damage the bone. Another reason is that the tissue loss due to evaporation as well as collateral damage is too large and suture of tissue at the end of the procedure is not practically feasible. A CO2 laser with a wavelength of 10.6 microns is not precise enough to perform some major applications such as first stage bone exposure, although it is suitable for various other applications. Yet, as already mentioned, its residual thermal damage, which is usually greater than 150-200 microns, renders this laser risky if not used with extreme care.
Although the 10.6 microns CO2 laser has been used in the oral cavity by dentists and oral surgeons for over 20 years, the isotopic 13C16O2 carbon dioxide laser which emits radiation at 11.2 microns has never been used in dentistry or in oral maxillofacial surgery. Companies which sell CO2 lasers for dentistry, such as Opusdent, sell 10.6 microns lasers and do not market 13C16O2 isotopic lasers which operate at a 11.2 microns wavelength for dentistry or oral surgery.
In contrast, the utilization in dentistry of an other wavelength emitted from regular 12C16O2 lasers, namely the 9.3-9.6 microns wavelengths range, is discussed in the prior art due to the enhanced absorption of that spectral range in hard tissue such as enamel, dentin or bone. [See “The Effect of the CO2 Laser (9.6 microns) on the Dental Pulp in Humans,” H. Wigdor et al, Lasers in Dentistry VI, Proceedings of SPIE, Volume 3910, San Jose 2000.]
A recent review of all the laser wavelengths used in dentistry appears in “An Overview of Laser Wavelengths used in Dentistry,” Coluzzi D. J, Dent. Clin North Am 2000 October; 44(4):753-65. Isotopic 13C16O2 lasers are not mentioned in that review.
Isotopic 13C 16O2 carbon dioxide lasers are lasers which emit radiation at 11.2 microns. The absorption of radiation at 11.2 microns wavelength is almost twice higher than at 10.6 microns. The absorption coefficient of radiation at 11.2 microns wavelength in water is 1370 cm−1, whereas the absorption at 10.6 microns is only 890 cm−1 (Irving and Pollack, Icarus, Vol. 8, No. 2, pp. 324-360, March 1968). The penetration depth in tissue is approximately 15 microns. U.S. Pat. No. 5,062,842 by Tiffany describes the use of an isotopic 13C 16 O2 laser in laparoscopic gynecology. The reason for using the isotopic laser in laparoscopy is the creation of a defocusing blooming effect by the normal 12C16O2 insuflation gas which absorbs the laser radiation produced by a normal 12C16O2 laser and the lack of such absorption when an isotopic 13C16O2 laser is used. An isotopic laser has been distributed by Coherent USA for gynecology.
Bone exposure in stage 1 of dental implantology is not performed with 12C16O2 lasers as explained earlier, although there would be a great advantage if that method of exposure were made possible. In bone exposure it is important to incise the soft tissue and the periostum tissue with negligible deterioration of the surrounding tissue or tissue loss so that it would be possible to suture the wound after bone drilling and minimize healing time of the soft tissue. Tissue loss should be minimal. It would be of great advantage to use a laser with the precision of a scalpel (which is currently used), yet with less bleeding. A laser which has a penetration depth in tissue as low as 3 microns is the Erbium laser. However, it is impossible to precisely focus a multi-mode Erbium laser for precise incisions, and furthermore, bleeding is excessive with an Erbium laser. It would be preferable to use a laser which emits a beam that penetrates deeper in tissue than an Erbium laser beam in order to reduce bleeding, but considerably less than a 10.6 microns laser, which causes too much collateral damage in first stage bone implantology. The laser should also be focused with high precision. Also, since the required laser's penetration depth in tissue is less than with a 12C16O2 laser, it would also be possible to efficiently utilize superpulses with a shorter duration than currently used with 12C16O2 lasers in dentistry.
The use of such a laser would also considerably enhance the safety of procedures, including most gingival procedures, performed very close to hard tissue or ligaments surrounding the teeth, which should not be heated. Also exposure in second stage implantology would be improved.
An other dental procedure which has been described in the prior art is root canal sterilization with the aid of a laser. A laser beam delivered through a thin fiber is aimed at the root canal, resulting in the destruction of bacteria while making visits to the dentist for antibiotic sterilization unnecessary prior to filling. Nd:YAG lasers, as well as regular 12C16O2 lasers, have been used for that procedure. Also, Erbium lasers with a 3-micron penetration depth have been used. The 13C16O2 isotopic laser has never been described for that procedure. The reduction of the penetration depth by 50% as compared to 12C16O2 lasers considerably increases the bacteria temperature by a factor of 2 (bacteria are 1-10 microns large), resulting in a higher destruction efficacy, or in a reduction of the necessary power to perform sterilization.
The smaller penetration depth of a laser as described hereinabove has an additional advantage in few lingual procedures, such as the treatment of leukoplacia which is treated by superficial removal of lingual tissue with a scanner for example.
A procedure performed in aesthetic dentistry is gum resurfacing and gum depigmentation. The procedure currently necessitates an Erbium laser since it provides superficial ablation and only pigmented tissue should be removed without creating a scar. Very often, a dentist who owns a 12C16O2 laser will not purchase another laser specifically for gum resurfacing. The use of a 15-micron penetrating isotopic laser will provide both bloodless incisions with underlying safety to hard tissue and gum resurfacing capabilities.
Another oral application which requires a smaller absorption depth than that attained with regular 12C16O2 lasers is the treatment of taste buds and oral pockets which are the cause of bad breath (halitosis), such as on the surface of the tonsils.
It is clear from that there is a need for a laser with an absorption depth of approximately 15 microns in soft tissue for the applications of dentistry and oral maxillofacial surgery.
Hard tissue has been treated in the past with a conventional 12C16O2 laser without reasonable success. The main problem was the treatment of enamel. Treatment of dentin gave better results, although 9.6 microns is considered the preferred wavelength with 12C16O2 lasers for hard tissue. 13C16O2 lasers operating in the 11.2 microns band have never been used on hard tissue.
Fiber delivery systems are currently being used with the regular 12C16O2 lasers in a variety of medical applications, including oral applications. 13C16O2 lasers have been used in gynecology due to the insuflation problem mentioned earlier. The 13C16O2 lasers operating in the 11.2-micron band are used with a surgical laparoscope and focusing optics. The combination of an isotopic 13C16O2 lasers and fiber delivery systems have not been identified as useful in prior art.
12C16O2 lasers operated in the superpulse mode are extensively used in the treatments of vocal cords which require extreme precision. Comprehensive descriptions of the use of state of the art lasers in the treatment of vocal cords are presented in “Carbon Dioxide Lasermicrosurgery of Bening Vocal Fold Lesions: Indications, Techniques and Results in 251 patients,” Remacle M et al, Ann Otol Rhinol Laryngol, February 1999, 108(2): 156-64 and in “CO2 Laser Surgery on Bening Lesions of the Vocal Cords,” Grossenbacher R, Adv Otholaryngology, 1995, 49: 158-61. The use of an isotopic 13C16O2 laser with only 15 microns penetration depth and possible shorter pulse duration associated with shorter tissue relaxation time for shorter penetration depth and smaller collateral damage has not been identified in the prior art.
An object of the invention is to provide dentists and oral maxillofacial surgeons with an incision tool to be used in the oral cavity, which enables a quick, bloodless and precise incision of soft tissue in the vicinity of hard tissue, without causing excessive damage to adjacent or underlying tissue, and without causing excessive tissue loss.
An object of the invention is to provide a laser for use in the oral cavity which emits radiation which penetrates approximately 15 microns in soft tissue.
An additional object of the invention is to considerably enhance the precision of laser surgery in dentistry and oral maxillofacial surgery, when compared to the precision attained by conventional 12C16O2 lasers operated at 10.6 microns.
An additional object is to provide dentists and oral maxillofacial surgeons with a laser which can efficiently perform Stage 1 bone exposure in dental implantology by laser incision of soft tissue and the periostum with good tissue preservation and minimal tissue loss, without significant bleeding and damage to the underlying bone.
An additional object is to provide dentists and oral maxillofacial surgeons a laser which allows for incisions of the gingival close to the hard tissue of the teeth or ligaments surrounding the teeth.
An additional object is to provide dentists with a tool which can clear gum pigmentation.
An additional object is to provide oral maxillofacial surgeons with a tool for superficial ablation of tissue on the tongue to treat leukoplakia.
Yet an additional object of the invention is to allow for the treatment of taste buds or pockets which are responsible for bad breath.
Yet an additional object is to provide a laser which is considerably more effective for the sterilization of a root canal than a 12C16O2 laser.
Yet an additional object of the present invention is to treat vocal cords with a higher precision than attainable with a 12C16O2 laser.